Hello, newbie here. my newest vw diesel is a 2000 Jetta with 90k miles on it. since it was at 90k, I did a timing belt swap and converted it to run on WVO and drove it for a while (8k). started hearing a ticking that I assumed to be a sticky lifter. it would tick for a while and then go away for a couple days. couple weeks later, my oil light comes on. pulled over and checked oil level and it was ok. didn't here any lifter noise common to loss of oil pressure so I drove it home (10 miles). started digging and found huge amounts of sludge in the oil. worst I've ever seen. every part in engine was coated, filter entirely plugged. turns out I bought a filter and oil when I got the timing belt and did an oil change on my gf's car but forgot to change mine! So, kicking myself, I did an oil flush and change. started it and light didn't come on and didn't hear anything so drove to work. light came on again just before work and ticking started faintly. drove slowly the last mile and ticking got louder. towed the car home. pulled pan and sure enough, the oil pick up was plugged with sludge. spent the next several hours cleaning sludge out of the engine. pulled out a couple pints worth! closed up engine and ran two batches of cheap oil mixed 50/50 with diesel through the engine to clean it. worked well and oil pressure is now good (30psi at idle). but, ticking is still there and even louder the ticking sounds like lifter noise still and not all lifters, just one I think. also, the ticking gets quieter as I increase rpm's and is not noticeable above 2500. listened with stethoscope and seemed to come from #4 right about where the lifter would be. I pulled the injector line and ran it to a bucket and ran the engine for a bit on the other three cylinders and ticking was still there so not the injector. today I pulled the cam and lifters out. how do I tell if they are bad? how do I check and clean them? or should I just replace? they look great and have no wear on them or the cam so I'd hate to replace them if they aren't the issue. I found some promising threads on here when i search but cant view until I post so, here's my post! Thanks!